The present invention relates generally to the production of Langmuir-Blodgett films and more particularly to the production of Langmuir-Blodgett films having photo-electronic properties.
The Langmuir-Blodgett technique has been used for many years to form monolayer or monomolecular films. Generally speaking, the Langmuir-Blodgett technique involves filling an open basin with a liquid subphase typically comprising a quantity of water and/or a water-miscible solvent. A small number of molecules, each molecule typically having a hydrophilic head group and a hydrophobic tail, are then deposited at the air-subphase interface. The molecules orient themselves at the air-subphase interface so that the hydrophilic head groups are in contact with the subphase and the hydrophobic tails are projected into the air. Because only a small number of molecules are typically spread over the air-subphase interface, the molecules are initially separated far apart relative to one another. A movable barrier in the basin is then used to compress the air-subphase interface until the molecules disposed thereat arrange themselves in an ordered, two-dimensional lattice. This lattice, which takes the form of a monolayer film, is then typically removed from the basin by deposition on a desired substrate. Frequently, more than one monolayer is constructed in this manner, the monolayers being used to form a multi-layered laminate.
In "Specific Recognition and Formation of Two-Dimensional Streptavidin Domains in Monolayers: Applications to Molecular Devices," Thin Solid Films, Vol. 180, pp. 93-99 (1989), which is incorporated herein by reference, M. Ahlers et al. describe the formation of a biotinlipid-streptavidin system, which is shown to bind and self-organize spontaneously to give thin two-dimensional crystalline layers of functional proteins at lipid-water interfaces. The streptavidin used was statistically labelled with two molecules of fluorescein isothiocyanate per molecule of protein according to a standard labelling procedure. The authors propose that the two biotin binding sites on the underside of each streptavidin molecule can be used to build up multilayered complex structures through binding to biotinylated functional groups, enzymes, antibodies, and other proteins. The authors also propose that multilayers of streptavidin and multifunctional polymers can be formed via biotinylated rigid or flexible couplers.
In an abstract entitled "Oriented Fluorescent Streptavidin-Phycoerythrin Conjugated Protein Monolayers on Biotin Lipid LB Monolayer Films," which was distributed to attendees of the Expanding Frontiers in Polypeptide and Protein Structural Research proceedings held in Whistler, British Columbia on Jul. 23, 1990, and which is incorporated herein by reference, L. Samuelson et al. describe oriented monolayer films possessing well-behaved isotherms, which are formed from biotin derivatized lipids by Langmuir-Blodgett techniques. In particular, the authors discuss how both avidin and streptavidin phycoerythrin conjugates, in an aqueous subphase, were found to interact preferentially with biotinylated lipid monolayer films while at the air-water interface and how the films exposed their hydrophilic biotin containing head groups to the four biotin binding sites on avidin and streptavidin in the conjugated proteins to form lipid-protein complexes having the effective stability of covalent bonds.